Handbrake mechanisms for applying and releasing the handbrake of a railway car have been in wide use. Examples of such handbrake mechanisms and improvements thereon are described in U.S. Pat. No. 3,040,597 to Frank E. Bretz, Jr. issued Jun. 10, 1962; U.S. Pat. No. 3,602,063 to William F. Koehler, issued Aug. 31, 1971; U.S. Pat. No. 3,714,842 to William F. Koehler, issued Feb. 6, 1973; and U.S. Pat. No. 3,933,225 to Frank E. Bretz, Jr., issued Jun. 10, 1974, the contents of these four patents being incorporated by reference herein.
U.S. Pat. No. 3,040,597, describes a handbrake mechanism for use with railway cars that has a combination of a rotary chain winding drum and a main gear wheel, with a rotatable hand wheel shaft having a bearing section at one end and a hand wheel receiving section at the other end. A ratchet wheel is provided intermediate the ends of the shaft and is rotatable with the shaft, and a ratchet pawl cooperates with the ratchet wheel to prevent reverse rotation of the ratchet wheel. A pinion is freely rotatably mounted on the bearing section of the shaft which engages the main gear wheel, the pinion having a radially extending flange rotatable cojointly therewith. A disengageable driving connection between the flange and the ratchet wheel is provided. A rotatably mounted trip bar cooperates with the flange to move the flange to disengage the driving connection with the ratchet wheel, so as to permit the pinion to freely rotate and release the main gear wheel for rotation in a brake releasing direction. A rotatably mounted trip cam cooperates with the trip bar to rotate the trip bar for shifting the flange, and an arm on the trip cam is arranged and adapted to overlie the flange and prevent shifting of the flange out of operational connection with the ratchet wheel when the trip cam occupies its non-operative position. The trip cam described in U.S. Pat. No. 3,040,597 is formed as a shaft with journaled ends, one of which ends is noncircular. A cam arm extends radially from the shaft, which cam arm engages a flange on a trip lever of the trip bar to shift the flange on the pinion and permit the chain to unwind from the chain winding drum to release the brakes. A safety arm is formed integrally with the shaft of the trip cam and normally extends in overlying relation with the flange on the pinion, the safety arm having a flared end which facilitates movement into a position where the safety arm is positioned to prevent movement of the flange on the pinion out of driving connection with the ratchet wheel. When the trip cam is rotated to move the cam arm into operative engagement with a blange on the trip bar, the safety arm is moved out of the path of the flange on the pinion and it is permitted to move, so as to provide for release of the ratchet wheel.
In U.S. Pat. No. 3,602,063, a handbrake mechanism is described having a square chain-winding drum. The square drum has a radial flange that is secured by rivets to a main gear, both of which are rotatably mounted on a shaft extending between a cover and a brake plate of a handbrake mechanism case. The square drum has an outer square configuration and an inner square configuration tangentially related to the outer square configuration. Alternate links of a chain are arranged to lie flatwise along the sides of the outer configuration while the intermediate links are positioned along the sides of the inner square configuration and at right angles to the axis of rotation of the square drum. Radially extending ribs having flat outer surfaces are formed at the ends of the sides of the inner square configuration, with concave end portions of the sides of the inner square configuration extending along the sides of the ribs which conform to the configuration of juxtaposed end portions of the intermediate links of the chain. The end of the chain opposite the end which is attached to the brake rigging is connected, in one embodiment, using a two-way handbrake mechanism, by a pin to a chain anchor that is secured to the case of the handbrake mechanism. In another embodiment, using a quick release handbrake mechanism, that end is connected to a shock-absorbing anchor means including an angle bracket bolted to the car frame, such as an end sill or other frame part of the car with which the braking mechanism is used.
In U.S. Pat. No. 3,714,842, an improvement over the handbrake shown in U.S. Pat. No. 3,040,597, is described where the trip bar of the handbrake mechanism uses a tie bar having a lever at each end for releasing the driving combination between the ratchet wheel and the gear wheel rotatable with a chain winding drum. Each lever has a pivot aperture for receiving a pivot pin that extends inwardly from the housing side wall. Each pivot also has an annular groove for receiving a U-shaped slot in a plate-like pin keeper adjacent the respective side wall of the housing to hold the pivot pin in operative position. Each keeper pin has a cylindrical spring guide to receive a coil compression spring that biases the respective lever to maintain the driving connection.
U.S. Pat. No. 3,933,225 discloses a similar railway car handbrake mechanism that uses one or more blocks of a compressible shock absorbing solid material or a compressible shock-absorbing spring to absorb the kinetic energy shock incident to the trip release of the chain under tension. The shock-absorbing device is located in the brake mechanism housing, in the path of the chain when the brake is released. The chain is prevented from winding in the wrong direction and causing damage to the handbrake mechanism at one end of the chain and brake components at the other end of the chain.